Block cave ore reserves: Are we reporting a reserve or potential inventory?

Abstract

Over the past 20 years, block cave operations have pushed the technical frontiers of caving mechanics by mining stronger rock masses, going deeper, extracting taller cave columns and demanding higher productivity rates. The methods and practices for the reporting of block cave ore reserves may not adequately allow for technical uncertainties in these complex and geotechnically challenging conditions. The actual performance of caving operations can vary significantly due to various technical, mining and economic factors. The ability to generate an ore reserves which is convincing has its challenges, particularly at conceptual and pre-feasibility levels when orebody access is generally unavailable to confirm the geotechnical environment that supports the parameters and assumptions that underpin block cave reserves. This paper considers whether current practices meet the guidelines required by industry reporting Codes, and why some operations struggle to meet initial reserve forecasts. Some ideas are offered in how technical risks can be better incorporated into establishing a credible base case scenario.